Carbon nanotubes (CNTs) possess many beneficial properties, such as exceptionally high strength and modulus, large elastic strain, and fracture strain sustaining capability, which are not available in the previous materials. Carbon nanotubes are the strongest fibers that are currently known. The Young's Modulus of single-walled carbon nanotubes is around 1 TPa, which is 5 times greater than steel (200 GPa) while the density is only 1.2-1.4 g/cm3. The tensile strength of single-walled carbon nanotubes falls in the range of 50-200 GPa. Theoretically, materials made of carbon nanotubes may be made lighter and stronger than that of state-of-the-art high-performance carbon fiber reinforced polymer composites, and would therefore be useful in structural and other applications.
Despite the tremendous potential of CNT materials, however, current CNT materials have been unable to fully realize the high-performance potential of CNTs composites. Some of the obstacles to realizing the high performance potential of CNTs composites include: (1) low CNT concentration; (2) poor CNT dispersion; (3) lack of CNT orientation; (4) weak interfacial bonding between CNT and matrix; and (5) short length of CNT (usually 1-100 μm) and limited aspect ratio for load transfer. New methods and materials are therefore needed to overcome these deficiencies and more successfully exploit the useful properties of CNTs.